Synthetic thermoplastic high molecular weight polyamides are made by the condensation of aminocarboxylic acids or by heating diamines with dibasic acids, as is well known and shown by U.S. Pat. Nos. 2,071,250; 2,071,253 and 2,130,948. These end products have been used to prepare fibers, films, bristles, felts, adhesives, molded engineering objects, etc.
It is well known that polyamides such as nylon-5, nylon-6, nylon-8, and nylon-12 have been produced by ring-opening polymerization of appropriate lactams. Nylon-6, also called polycaprolactam, was originated by I. G. Farbenindustrie in 1940. In one preparation technique, the polymerization of .epsilon.-caprolactam (also known as .epsilon.-aminocaprolactam or simply caprolactam), is carried out by adding water to open the ring and then removing water again at elevated temperature, where linear polymer forms. Caprolactam may also be polymerized by ionic chain mechanisms.
Nylon-6 has properties similar to nylon-66, but has a lower crystalline melting point and is somewhat softer and less stiff. The major use for the polymer is in tire cord. Polycaprolactam accounts for about 25% of U.S. consumption of nylon.
Attempts are constantly being sought for the improvement of these polymers. For example, a few years after the invention of nylon 6,6 made from hexamethylene diamine and adipic acid, it was discovered that substitution of a portion of hexamethylene diamine with triethyleneglycol diamine gave polyamides with better dye receptivity and enhanced water absorption, as shown in U.S. Pat. Nos. 2,359,867 and British Patent 562,370. An excellent example of how comfort and feel can be added to nylon 6 type polyamides has been described by R. A. Lofquist, et al., "Hydrophilic Nylon for Improved Apparel Comfort," Textile Research Journal, June 1985, p. 325-333. These authors copolymerized caprolactam with polyethyleneoxy diamines and dibasic acids such as terephthalic acid. Comfort-related tests revealed that fabrics made from such fibers are superior to those from polyesters and polyamides. See also U.S. Pat. No. 4,919,997 for a description of water-absorbing mats made using these techniques. The melt-blown water-absorbing mat of fibers of this patent comprise a block copolyetheramide having polyether and polyamide segments. The JEFFAMINE.RTM. ED-Series amines were used as the amine-terminated polyethylene oxide glycols by Lofquist, et al. to produce a modified nylon-6. These amines are high molecular weight (600 to 2000) alkylene glycol diamines having the formula H.sub.2 NRNH.sub.2, where the radical R is a polyoxyalkylene chain of molecular weight of from about 200 to about 4000 having terminal carbon atoms to which nitrogen atoms are bonded. Moisture absorption was found to be greatest using the amines having the highest molecular weight.
Also of interest is S. W. Shalaby, et al., "Copolymerization of Caprolactam with Polyoxybutylene Diamine," Polymer Engineering and Science, March, 1973, Vol. 13, No. 2, pp. 88-95. This article describes that nylon 6-polyoxybutylene block copolymers were prepared by reacting polyoxybutylene diamine with caprolactam in the presence of phosphoric acid. The copolymerization was carried out in a Helicone-type reactor and the effect of time, temperature and caprolactam concentration on the properties of the products was recorded. Differential Scanning Calorimetry (DSC) studies of the products suggested the presence of both the ABA and AB types of sequences, where A and B represent nylon 6 and polyether blocks, respectively. Dynamic mechanical measurements of typical copolymers revealed the presence of at least two different nylon moieties. The melt rheology data reflected a general increase in the pseudoplasticity of the copolymer with the increase of the polyether content. Increases of the polyether content in the copolymer resulted in an increased elongation and a decreased tensile strength and modulus.
Similarly, the copolymerization of laurolactam with poly(oxybutylene)diamine was achieved by the same authors by allowing the reactants to react in the presence of phosphoric acid at 220.degree.-275.degree. for 3-24 hours, as reported in S. W. Shalaby, et al., "Nylon 12--Poly(oxybutylene) Block Copolymers," Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 2, 1973, pp. 128-132. The effect of reaction conditions on the conversion and the composition of the copolymers was measured. The structure of the copolymers was determined by conventional methods, including infrared, X-ray and DSC techniques. The DSC data suggested the presence of both the ABA and AB types of sequences, where A and B represent nylon 12 and poly(oxybutylene) blocks, respectively. The copolymers were shown to have higher elongation and lower modulus than nylon 12 and became more flexible and ductile as the weight fraction of the poly(oxybutylene) block increased.
Modified nylon 6 polymers may be prepared with improved mechanical properties by polymerizing .omega.-lactams with a polyisocyanate blocked with .omega.-lactam, a polyoxyethylene diamine and an alkali lactamate, as a catalyst salt, as described in European Patent Application 0324432.
See also European Patent 0 163 902 A1 which relates to high polymerization degree polyetheresteramides having no gelated materials and superior color tones. These polyamides are apparently quickly obtained through the polycondensation reaction carried out between (a) one or more than two polyamide forming components selected from lactams and aminocarboxylic acids as well as the salts of substantially equal quantities of diamines and dicarboxylic acid, and (b) the polyetherester forming components consisting of substantially equal quantities of dicarboxylic acids and poly(alkylene oxide) glycols, in the presence of 0.001 to 0.5 percent by weight of the mixtures composed of antimony oxides/organic tin compounds, and more preferably, in the co-presence of 0.0005 to 0.5 percent by weight of phosphoric compounds.
U.S. Pat. No. 3,454,534 indicates that the hydrophilic characteristics of nylon-66 may be improved by adding a polyalkylene glycol diamine to the molten polymer prior to spinning. The process involves producing polyhexamethylene adipamide where equimolar proportions of adipic acid and hexamethylene diamine are reacted together to form molten polyhexamethylene adipamide. The improvement involved introducing from about 0.3 to 3.0 weight percent of a polyalkylene glycol diamine into the molten polymer subsequent to polymer formation and prior to spinning. The polyalkylene glycol diamine has the formula: H.sub.2 N--(CH.sub.2).sub.3 --O--[R--O].sub.x --(CH.sub.2).sub.3 --NH.sub.2 where R is an alkylene hydrocarbon radical having a chain length of from 2 to about 8 carbon atoms, and x is an integer sufficiently large to confer a molecular weight of at least 1000. Note that propylene linkages are required and that the polyalkylene glycol diamine must have a molecular weight of at least 1000.
Block copolymers of poly(oxa-amide) and polyamide are described in U.S. Pat. Nos. 4,113,794; 4,130,602 and 4,136,133. The '794 patent discusses novel copolymers formed by melt blending a melt spinnable polyamide, such as nylon-6, and a block of random poly(dioxa-amide), such as a copolymer prepared from the mixture of caprolactam and the salt of adipic acid and 4,7-dioxadecamethylene diamine. Block copolymers formed by melt blending a melt spinnable polyamide such as nylon-6 and a poly(dioxa-amide) such as poly(4,7-dioxadecamethylene adipamide) is disclosed in the '602 patent. The '133 patent teaches block copolymers formed by melt blending a melt spinnable polyamide such as nylon-6 and a poly(oxa-amide) such as poly(4-oxaheptamethylene adipamide). As examples only, in the '133 patent, the poly(oxa-amide) groups have the formula: ##STR2## where R.sub.1, R.sub.2 and R.sub.3 are hydrogen, C.sub.1 -C.sub.10 alkyls and C.sub.3 -C.sub.10 isoalkyls; R.sub.4 is selected from the group consisting of C.sub.0 -C.sub.10 alkylenes and C.sub.3 -C.sub.10 isoalkylenes, where y may range from 4 to 200. All of these materials are noted to have utility as fibers.
U.S. Pat. Nos. 4,044,071 and 4,045,511 describe methods for making the copolymers discussed in the previous paragraph. The '071 patent teaches a process for forming block copolymers by mixing a dry salt of a prepolyamide and a molten melt-spinnable polyamide. The mixture is heated to a temperature in the range of between the melting point of the higher melting component of the mixture to below the amide-interchange temperature of a blend of the melt-spinnable polyamide and the homopolymer which would result from the polymerization of the salt. Mixing and heating is continued until substantially all of the salt and the polyamide are converted into a block copolymer. The '511 patent teaches a similar process, but one that is lower in energy and uses a blend of dry particles of a melt-spinnable polyamide, rather than using the polyamide in the molten state.
U.S. Pat. No. 4,297,454 teaches a method for preparing a block copolymer of an ether-free polylactam and a polyetheramide, e.g., poly(4,7-dioxadecamethylene adipamide) involving polymerizing a lactam, e.g., caprolactam, in contact with the polyetheramide. At least one of the lactams and the polyetheramide are molten during the lactam polymerization and block copolymer formation. The materials prepared appear similar to those described in U.S. Pat. Nos. '794; '602 and '133, described above. Examples of polyetheramides mentioned in the '454 patent include poly(4,7-dioxadecamethylene adipamide), poly(4,7-dioxadecamethylene sebacamide), poly(4,9-dioxadodecamethylene adipamide), poly(4,8-dioxa-6,6-dimethylundecamethylene adipamide), poly(4,7-dioxa-2,9-dimethyldodecamethylene adipamide), poly(4,7-dioxadecamethylene-2-methylene adipamide), poly(4-oxaheptamethylene adipamide), and poly(4-oxa-2,6-dimethylmonomethylene adipamide).
Two patents, U.S. Pat. Nos. 3,972,961 and 4,017,557 relate to graft copolymers where the side chain polymers to be added to the trunk copolymers come from reactions of caprolactam with compounds having a single reactive amine site. The '961 patent describes these side chain polymers as: ##STR3## where R.sub.1 is hydrogen or C.sub.1 to C.sub.18 alkyl; R.sub.2 is C.sub.1 to C.sub.18 alkyl, aralkyl, e.g. benzyl; aryl, e.g., phenyl; or R.sub.1 and R.sub.2 taken together constitute a 5 or 6-membered ring; r and p are integers; r is preferably 3-11 and p is preferably 4-29. The '557 side chain polymer structure is more complex.
The '961 patent describes a process for the preparation of thermoplastic graft copolymers which comprises heating for about 15 seconds to 60 minutes, with mixing, a trunk copolymer of at least two monomers, at least one of said monomers providing amine-reactive sites taken from the group consisting of the anhydride group, e.g., maleic anhydride; a vicinal pair of carboxylic groups and a carboxylic acid adjacent to an alkoxycarbonyl group, wherein the alkoxy group contains up to 20 carbon atoms, and at least one of said monomers containing no amine-reactive sites, and at least one side chain polymer having per chain one active amine site taken from the group consisting of primary and secondary amines, the remainder of said side chain polymer being substantially unreactive with the reactive sites, e.g., amino-substituted polycaprolactam, polylaurolactam, polyethylene oxide, etc., of the trunk copolymer. The process provides control of the type and length of the side chain polymer grafted onto the trunk copolymer. Plastic graft copolymers are included, specifically those containing one or more side chain polymer types with the proviso that when only one type of side chain polymer is present the side chain polymer contains only one nitrogen atom, said atom being found in the active amine site.
The U.S. Pat. No. 4,017,557 teaches 6-nylons and 12-nylons having primary amino end-groups and an average degree of polymerization of about 5-60 may be grafted onto elastomeric trunk polymers having anhydride groups, vicinal carboxylic groups, or carboxylic groups adjacent to alkoxycarbonyl groups by heating a mixture of the nylon and the trunk polymer, preferably under high shear conditions for about 1 minute or less to 30 minutes or more above the melting temperature of the nylon. The resulting elastomeric graft polymers are suitable for fabricating into a variety of articles, such as, for example, wire jacketing, hose, belts, seals, gaskets, and low pressure tires.
L. Z. Chung, et al., "Block Copolyetheramides. II. Synthesis and Morphology of Nylon-6 Based Block Copolyetheramides," J. Polym. Sci. Part A: Polym. Chem., Vol. 30, 1992, pp. 951-953 describes a novel preparation method of nylon-6 based block copolyetheramides. The new approach avoids phase separation by an alternate route. Poly(tetramethylene) glycols (PTMEGs) were reacted with caprolactam in the presence of adipic acid.
U.S. Pat. No. 5,030,710 notes that novel modified nylon-6 may be produced by using a combination of one or more dicarboxylic acids and triethylene glycol diamine and tetraethylene glycol diamine. A dicarboxylic acid/polyethylene glycol diamine salt may be reacted with .epsilon.-caprolactam to provide the modified nylon-6. The diamines have the formula NH.sub.2 --(CH.sub.2 CH.sub.2 O).sub.x --CH.sub.2 CH.sub.2 --NH.sub.2, where x ranges from 2 to 3. Surprisingly, the suitable diamines include triethylene glycol diamine (x=2; JEFFAMINE.RTM. EDR-148 Amine) and tetraethylene glycol diamine (x=3; JEFFAMINE.RTM. EDR-192 Amine), but not closely related bis-aminoethyl ether (x=1; BAEE). Unexpectedly, BAEE, which only differs from JEFFAMINE EDR-148 Amine by one --(CH.sub.2 CH.sub.2 O)-- group, did not give satisfactory product -- the fibers were too weak. The resulting modified nylon-6 polymers of the invention, however, including fibers therefrom, have improved water absorbancy properties and greater flexibility. Polyamide products with a wide range of water adsorbancies may be obtained by adjusting the amount of amide.
Finally, it is known to use monoamines and diamines to effect the polymerization of caprolactam. These amines do not contain ether groups and are taught as initiators and not as reactive modifiers. See, for example, T. G. Majury, "Amines and Carboxylic Acids as Initiators of Polymerization in Caprolactam," Journal of Polymer Science, Vol. 31, 1958, pp. 383-397, where this phenomenon is studied using benzylamine and hexamethylenediamine. There is also G. M. Burnett, et al., "Polymerization of Caprolactam. I. Initiation by Amines," SCI Monograph No. 20: The Chemistry of Polymerization Processes, 1966, pp. 139-156, which discusses the study of the polymerization of .epsilon.-caprolactam by dilatometry in the temperature range 200.degree.-230.degree. using a variety of organic amines and amine hydrochlorides as initiators.
Although nylon-6 has been incrementally improved as shown by the publications discussed above as examples, there remains a need for new polyamides having a lower modulus, but which retain the beneficial properties of the original polyamide materials, in this case, nylon-6. In particular, it is desirable to retain the higher use temperatures as compared with currently available polyether amide segment block copolymers.